1. Field of the Invention
The present invention relates to a system having a plurality of memory devices. More particularly, the present invention relates to a method for establishing an interface between a host and a plurality of memory devices of a system that utilizes a Multimedia Card (MMC) or Secure Digital (SD) protocol according to an interleaving scheme.
2. Discussion of Related Art
With advancements in storage media technology, various types of memory have recently been manufactured as auxiliary storage for portable electronic devices such as mobile phones and digital cameras. Examples of these types of memories include compact flash, Multimedia Cards (MMC), Smart Media Cards (SMC), and Secure Digital (SD) cards. Because these memory devices are small and light, they are suitable as data storage in portable electronics.
Generally, memory devices are coupled to a host (e.g., a computer) via a system bus. The memory devices and the host use a predetermined communication protocol (e.g. MMC or SD) to establish data communication therebetween. FIG. 1 is a diagram illustrating a conventional interface system between host 10 and a plurality of memory devices 20-1 through 20-nthat utilizes a general MMC or SD protocol. Host 10 is connected to memory devices 20-1 through 20-nvia system bus 30 and may be individually controlled by host 10. The memory devices 20-1 through 20-n and the host 10 communicate using a predetermined protocol stored in host 10. In a system using MMC or SD card specifications, the operating mode of each of the memory devices 20-1 through 20-n may include a card identification mode and a data transfer mode.
In the card identification mode, host 10 may request each of the memory devices 20-1 through 20-n to provide a card identification number (CID number). If a memory device card (e.g. first memory device 20-1) among the memory devices 20-1 through 20-n successfully responds to the request from host 10, host 10 then allocates a Relative Card Address (RCA) to the first memory device 20-1. If the RCA is allocated to first memory device 20-1, the first memory device 20-1 enters the data transfer mode. In the data transfer mode, first memory device 20-1 may be in various states, such as a stand-by state, a transfer state, a sending data state, a receiving data state, and a programming state.
In general, in a system that utilizes the MMC or SD protocol, only a memory device among the memory devices 20-1 through 20-n that enters the transfer state performs an operation (e.g., a write operation) in response to operating commands (write commands, etc.) received from host 10. For example, the memory devices other than the first memory device 20-1 are in the stand-by state when first memory device 20-1 is in a program busy state. That is, host 10 does not transmit commands or data necessary to perform the write operation to any one of the memory devices other than memory device 20-1 until the end of the busy time of the write operation performed by first memory device 20-1. In addition, if host 10 checks whether the busy time ends by using a polling method, the process increases the load on host 10. Accordingly, there is a need for a method and system for allowing the host to rapidly and efficiently establish an interface with each of the memory devices.